We have established that pretreatment with acetazolamide (Diamox) exerts a unique protective action against the convulsive threshold of the X-Ray contrast agent sodium diatrizoate (Hypaque) in the rabbit. In our preliminary studies directed at understanding the mechanism of this protection we found that Diamox reduces the amount of radioactively labeled contrast agent present in the cerebrospinal fluid after ten minutes following its intracarotid administration in an angiographic dose by 43 percent. On the basis of these findings we propose to conduct a larger study employing the methylglucamine salts of iodothalamate (Conray) and diatrizoate (Meglumine Hypaque), which are now more widely used than the sodium salts in cerebral angiography, to document the most favorable dose/tim relationships for Diamox premedication as determined by the quantity of transferred contrast agent appearing in the cerebrospinal fluid per unit time. Our purpose is to prepare a protocol for its application to prevent neurological complication arising during or after cerebral and vertebral angiography, particularly in the high risk patient.